Two tetralkylated phenylenediamines (TAPD) 1 and 2 have been prepared by reductive alkylation of para-dimethylaminoaniline with furfural or thiophene 2-carboxaldehyde, respectively. Their chelation ability has been evaluated as electrochemical guest-responsive chemosensors for Cd(II) in acetonitrile (ACN), dimethylformamide (DMF), propylene carbonate (PC), and nitromethane (NM). The voltamperometric studies showed that these compounds are able to bind the Cd(II) cation with strong affinities except in DMF. The redox features of the chemosensors changed drastically when they are bounded to Cd(II) to undergo important anodic potential peak shifts comprised between ca. 500 and ca. 900？mV depending on the solvent. The addition of ～4–10% molar triflic acid (TfOH) was found to be necessary to achieve rapidly the cation chelation which is slow without the acid. The electrochemical investigations suggested the formation of 1？:？2 stoichiometry complexes [Cd(L)2]2+. The results are discussed in terms of solvent effects as a competitive electron donating ligand to the cation. The reaction coupling efficiency (RCE) values were determined and were also found to be solvent-dependent. 1. Introduction Metallic ions are widely present in the biological systems and play many important roles [1, 2]. Some others are toxic but are tolerated at low levels such as nickel or cobalt because of their interventions in some biological processes [3]. Other cations can cause major health damage if they are present even in trace amounts such lead(II) and cadmium(II) [4, 5]. Indeed, lead is known to cause saturnism when it is present at high concentration in biological medium [6, 7]. Cadmium has been reported to block calcium channels in sensory neurons and prevents regular central system functioning [8]. Many researchers have been consequently devoted to the development of methods for the determination of these cations. In living organisms, biological receptors like those found in enzymes or neurons bind selectively to a cation to achieve some goals most of the times in reversible processes. Contrarily, most of the synthetic receptors do not work that way; they tightly bind to cations in nonreversible processes [9]. Only few attempts have been directed at the elaboration of reversible chemosensors useful for the detection and eventually the delivery cations such as calcium ions when they are photochemically or electrochemically triggered [10, 11]. The first class of chemosensors relies on chromogenic guest-responsive transducers whose properties change when they are linked to
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